Field of the Invention
The present application relates to a water-soluble cutting fluid for slicing silicon ingots.
Description of Related Art
When wire saws are used with the conventional cutting fluid for cutting silicon ingots, the surface refinement of the wafer is not satisfactory owing to the hardness of silicon ingots or insufficient lubricating capability of the conventional cutting fluid. Furthermore, as the cutting fluid is recycled during the cutting process of silicon ingots, disadvantages such as foaming have been reported.
Water-soluble cutting fluids have been proposed using, for example, the composition composed of polyalcohol such as propylene glycol or the like, aromatic polyprotic carboxylate salts (triethanolamine isophthalate or the like), alkylene oxide adducts of alkylene glycol such as polyethylene glycol or the like, and water (referring to the Patent reference 1).
In addition, in order to lower the danger of ignition and raise the cooling efficiency, the proportion of water of high specific heat is increased, which contributes to the erosion or tarnishment of the metal or wires used in the cutting apparatus.
The solutions for the above-mentioned issues have been developed by preparing the water-soluble cutting fluid with amine compounds to restrain erosion (referring to the Patent reference 2).
On the other hand, for preventing the generation of hydrogen from the reaction of water and silicon, the water-soluble cutting fluid having the oxidizing agent capable of oxidizing the silicon tiny particles generated during the cutting process is developed (referring to the Patent reference 3).
However, although the reaction of water and silicon is inhibited, the erosion issues of the processing apparatus or the wire of the fixed abrasion grain wire still exist.
Furthermore, during the cutting process, for the purposes of cooling or lubricating the wire and the processed silicon ingots and cleaning the processed surface, the cutting fluid is supplied to the process site during processing. However, recycling the cutting fluid causes foaming, and the cutting fluid as well as the foam may overflow to contaminate the surroundings.
Possible plans can be listed as the method of adding defoaming agents to the retention tank or method of coating defoaming agents to the foam-overflown site, etc., but no satisfactory results are achieved yet.